This invention relates generally to surface mount packages, and more particularly, to surface mount packages for two terminal devices such as diodes.
Surface mount components or devices, and in particular, the use of surface mount packages allow smaller footprint designs with improved functionality and increased mounting densities. For example, Integrated Circuit (IC) mounting methods using surface mounting allow mounting of packages on both sides of, for example, a printed wiring board, thereby resulting in higher density mounting and reduced wire board size as compared to through-hole mounting. These surface mount packages also are becoming increasingly smaller and thinner to further provide this higher density mounting.
Surface mount packages include different isolated paths for electrical current flow, for example, to an anode and cathode within the packages. Plastic is often used to form the surface mount package and may be used to isolate the current flow. These surface mount packages are commonly referred to as plastic packages. Separate metal connection pads may be used to provide electrical connection to the anode and cathode. Further, vias, other conduits or sidewall metallization may be included to provide electrical and/or thermal continuity between top metal connection pads and backside metal connection pads of the surface mount package.
These surface mount packages may be used to mount thereon different types of two terminal devices, such as, for example, diodes, and more particularly, light emitting diodes (LEDs). However, operation of some of these two terminal devices generates high levels of heat. Plastic packages may not provide acceptable levels of thermal dissipation for some of these devices and for certain applications. For example, certain high power devices may require thermal dissipation at levels higher than can be provided using these plastic packages. Further, because plastic has a relatively high thermal resistance, the efficiency of devices mounted within these packages may be reduced.
Additionally, it is difficult, if not impossible, to seal the plastic packages for certain applications, for example, to hermetically seal the plastic packages. This is because at the higher temperatures needed to hermitically seal the package (e.g., 300-400 degrees Celsius solder temperature), the plastic packages can melt.
Thus, these plastic packages may not be suitable for certain applications and further may not provide acceptable operating characteristics.